Compact Tiltrotor Pylon-Conversion Actuation System

ABSTRACT

A tiltrotor aircraft having a wing and a rotatable pylon carried by the wing is disclosed. The pylon is secured to a pylon support spindle that extends into the wing. A link connects a radial portion of the pylon support spindle to a radial portion of a rotary actuator, such that the pylon support spindle is rotated as the actuator is rotated.

TECHNICAL FIELD

The present invention relates to tiltrotor aircraft. In particular, the present invention relates to compact pylon-conversion actuation system for a tiltrotor aircraft.

DESCRIPTION OF THE PRIOR ART

Tiltrotor aircraft are hybrids between traditional helicopters and traditional propeller driven aircraft. Typical tiltrotor aircraft have rotor systems that are capable of articulating relative to the aircraft fuselage. This articulating portion is referred to as a nacelle. Tiltrotor aircraft are capable of converting from a helicopter mode, in which the aircraft can take-off, hover, and land like a helicopter; to an airplane mode, in which the aircraft can fly forward like a fixed-wing airplane.

The design of tiltrotor aircraft poses unique problems not associated with either helicopters or propeller driven aircraft. In particular, the tiltrotor assemblies must be articulated between helicopter mode and airplane mode. To convert between helicopter mode and airplane mode the nacelle must rotate relative to the fuselage.

It is known in the art to use linear actuators, such as screw jacks or hydraulic jacks, to rotate the nacelle about a rotation point relative to the fuselage. Linear actuators tend to be bulky and extend outside the envelope of the wing or nacelle requiring fairings that extend beyond the preferred aerodynamic shape of the wing or nacelle. Another disadvantage when using linear actuators is that very high torque is required at the extremes of the systems movement. Most linear actuators have constant torque throughout the range of motion, but are arranged so that they have the least mechanical advantage at the extremes of the range of motion. Therefore, the linear actuator is larger than it needs to be for the majority of the range of motion so that it can be of sufficient size at the extremes.

Although there have been significant developments in the area of tiltrotor conversion actuation systems, considerable shortcomings remain.

SUMMARY OF THE INVENTION

There is a need for tiltrotor pylon-conversion actuation system that can provide the necessary torque at the extremes of the range of motion while also being compact.

Therefore, it is an object of the present invention to provide a tiltrotor pylon-conversion actuation system that can provide the necessary torque at the extremes of the range of motion while also being compact.

This object is achieved by providing a rotary actuator and link assembly to rotate the pylon, or nacelle, over the limited range of motion needed to convert a tiltrotor aircraft from airplane mode to helicopter mode, and vice versa. The pylon rotates about a pylon support spindle while a rotary actuator drives an actuator spindle parallel to the pylon support spindle. The pylon support spindle is connected to the actuator spindle by a solid link. The difference in diameter of the spindles provides an increase in torque at the extremes of the range of motion and the solid link provides a limit on the range of motion.

The present invention provides significant advantages, including: (1) providing a compact drive system that can be housed completely within the wing structure; (2) increased mechanical advantage at the extremes of the range of motion to match that closely match the needs of the application; (3) a rigid limit on the range of motion to prevent over-extension under severe conditions; and (4) rigid support to hold the pylon in whatever position the system has moved the pylon into.

Additional objectives, features, and advantages will be apparent in the written description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as, a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a tiltrotor aircraft in airplane mode;

FIG. 2 is a perspective view of a tiltrotor aircraft in helicopter mode;

FIG. 3 is a partial cutaway view of the end of a left wing of a tiltrotor aircraft incorporating an embodiment of a pylon-conversion actuation system according to the present invention, system being shown in conversion mode;

FIG. 4 is an enlarged cutaway view of the actuation system of FIG. 3 in conversion mode;

FIG. 5 is an enlarged cutaway view of the actuation system of FIG. 3 in airplane mode;

FIG. 6 is an enlarged cutaway view of the actuation system of FIG. 3 in conversion mode;

FIG. 7 is an enlarged cutaway view of the actuation system of FIG. 3 in helicopter mode;

FIG. 8A is a schematic view of the system linkage as shown in FIG. 5, in airplane mode;

FIG. 8B is a schematic view of the system linkage as shown in FIG. 6, in conversion mode;

FIG. 8C is a schematic view of the system linkage as shown in FIG. 7, in helicopter mode; and

FIG. 9 is a graph of the torque advantage of the actuation system of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention represents the discovery that a specific actuator system may be used to provide several benefits in rotating the pylon of a tiltrotor aircraft from airplane mode to helicopter mode. The actuator system according to the present invention is particularly useful in applications in which a compact system is needed to maintain the aerodynamic shape of the wing and pylon.

Referring to FIG. 1 of the drawings, a tiltrotor aircraft 11 is shown in airplane mode. In particular, aircraft 11 shown in FIG. 1 is an unmanned aerial vehicle (UAV), as opposed to manned vehicles, and therefore has no provision for onboard human pilots. The invention is not limited to UAVs and may be used on manned vehicles as well. Aircraft 11 has a fuselage 13 with wings 15 extending from the fuselage 13. At the ends of wings 15 are pylons 17, which rotate on the ends of wings 15 through a range of from about 90° of rotation up to about 100° of rotation. In a UAV such as aircraft 11, pylons 17 provide a rotatable support for rotors 19, and the engine used to power rotors 19 is located within the fuselage. In larger tiltrotor aircraft, such as a manned tiltrotor, engines may be located in pylons 17. When configured in airplane mode the plane of each rotor 19 is generally vertical and each pylon 17 is generally horizontal. While aircraft 11 is shown with pylons located at the ends of wings 15, other configurations may be used, such as a configuration in which the pylons are rotatably connected to the fuselage.

Referring now to FIG. 2 of the drawings, tiltrotor aircraft 11 is shown in helicopter mode. In helicopter mode the plane of each rotor 19 is generally horizontal and each pylon 17 is generally vertical.

Referring now to FIG. 3 of the drawings, the pylon end of a left wing 15 is shown in partial cutaway view. Wing 15 is shown with pylon-conversion actuation system 21 exposed, and pylon 17 is shown in phantom. Pylon 17 is in conversion mode, in other words, between helicopter mode and airplane mode.

Referring now to FIG. 4 of the drawings, the pylon end of left wing 15 of FIG. 3 is shown in cutaway view with actuation system 21 in conversion mode. Wing 15 is structurally comprised of skin 23 (shown in FIGS. 5 through 7) and structural ribs 25 (partially removed in FIG. 4 for clarity). Pylon support spindle 27 extends from the end of wing 15 through two ribs 25. Where the support spindle 27 passes through ribs 25 bearing housings 29 support spindle 27 and allow for axial rotation of spindle 27 about spindle axis 31. Spindle bracket 33 is on the outer circumference of support spindle 27 and provides a spindle connection point 35 for link 37. Link 37 is pivotally mounted to spindle bracket 33 at spindle connection point 35. Link 37 is a rigid, curved member, the curve allowing for a slight increase in range of motion than would be available if a straight member was used. A taller bracket 33 would allow use of a straighter link 37 at the cost of compactness.

Link 37 is pivotally mounted to bracket 33 at one end of link 37 with the opposite end of link 37 being pivotally mounted to rotary actuator 39 at actuator connection point 41. Rotary actuator 39 is supported by actuator bearings 43 on either side of rotary actuator 39. Actuator bearings 43 are supported by actuator support 45 (partially sectioned in FIG. 4). Actuator support 45 and actuator bearings 43 support rotary actuator 39 and allow rotary actuator 39 to rotate about actuator axis 47, which is parallel to spindle axis 31. Rotary actuator 39 is driven by electric actuator drive 49 to rotate about actuator axis 47, though a wide variety of types of actuator drives 49 may be used, including drives 49 using hydraulic power or electric motors.

Referring now to FIG. 5 of the drawings, the pylon end of left wing 15 is shown in cutaway view with actuation system 21 in airplane mode and actuator drive 49 removed. Input shaft 51 is shown extending from rotary actuator 39 through rib 25 to connect with actuator drive 49 (not shown in FIG. 5). Actuator drive 49 applies torque to input shaft 51, which is connected to rotary actuator 39 through a gear-reduction system (not shown), such as a planetary-gear system. This gear system multiplies the amount of output torque from actuator drive 49 and permits use of a smaller, lower-torque actuator drive 49. For example, a gear system may provide for a 50:1 ratio of revolutions of shaft 51 to revolutions of rotary actuator 39.

In the embodiment shown input shaft 51 extends through the last rib 25 of wing 15 towards pylon 17. This allows the actuator drive 49 to be easily accessed when pylon 17 is removed. Alternatively, input shaft 51 may extend into wing 15, away from pylon 17, allowing actuator drive 49 to be accessed by removing a portion of skin 23.

Continuing with FIG. 5 of the drawings, the actuation system 21 is shown in airplane mode. Rotary actuator 39 is rotated forward (counter-clockwise as shown from the end of left wing 15) such that link 37 is generally adjacent the circumference of spindle 27 and spindle 27 is rotated forward such that pylon 17 is in airplane mode.

Referring now to FIG. 6 of the drawings, a cutaway view of the pylon end of left wing 15 shows actuation system 21 in conversion mode, which is any position between the airplane mode and helicopter mode positions. In order to move from the airplane mode shown in FIG. 5 to the conversion mode shown in FIG. 6, actuator drive 49 applies a torque to input shaft 51 to rotate rotary actuator 39 backward (clockwise as shown from the end of left wing 15) about actuator axis 47. This puts link 37 in tension and thereby creates a torque on pylon support spindle 27, rotating pylon support spindle 27 backward (clockwise as shown from the end of left wing 15) about spindle axis 31 to put pylon 17 into conversion mode.

Referring now to FIG. 7 of the drawings, a cutaway view of the pylon end of left wing 15 shows actuation system 21 in helicopter mode. In order to move from the conversion mode shown in FIG. 6 to the helicopter mode shown in FIG. 7, actuator drive 49 applies a torque to input shaft 51 to rotate rotary actuator 39 further backward (clockwise as shown from the end of left wing 15) about actuator axis 47. This puts link 37 in tension and thereby creates a torque on pylon support spindle 27 to rotate the pylon support spindle 27 further backward (clockwise as shown from the end of left wing 15) about spindle axis 31 to put pylon 17 into helicopter mode.

Referring now to FIGS. 8A, 8B, and 8C of the drawings, each is a schematic of the linkage of pylon-conversion actuation system 21. The schematics are in the plane normal to spindle axis 31 and actuator axis 47, spindle axis 31 and actuator axis 47 being parallel, as described above. Therefore, spindle axis 31 and actuator axis 47 are represented as points in FIGS. 8A, 8B, and 8C. Also, spindle connection point 35 and actuator connection point 41 are shown as points at either end of link 37 as described above. Rotary actuator 39 rotates about actuator axis 47 and pylon support spindle 27 rotates about spindle axis 31. Actuator connection point 41 rotates about actuator axis 47 and spindle connection point 35 rotates about spindle axis 31. Link 37 maintains a fixed distance between spindle connection point 35 and actuator connection point 41, thereby causing spindle connection point to rotate in reaction to the rotation of actuator connection point 41, as shown in FIG. 8A, 8B, and 8C.

FIG. 8A is a schematic of the linkage of actuation system 21 in airplane mode. Rotary actuator 39 is rotated counter-clockwise until link 37 has pushed pylon support spindle 27 to rotate counter-clockwise into airplane mode.

FIG. 8B is a schematic of the linkage of actuation system 21 in conversion mode. Rotary actuator 39 is rotating and link 37 is causing spindle 27 to rotate in the same direction as rotary actuator 39. As compared to FIG. 8A, rotary actuator 49 has rotated clockwise, thereby causing spindle 27 to rotate clockwise toward helicopter mode. As compared to FIG. 8C, rotary actuator 49 has rotated counter-clockwise, thereby causing spindle 27 to rotate counter-clockwise toward airplane mode.

FIG. 8C is a schematic of the linkage of actuation system 21 in conversion mode. Rotary actuator 39 is rotated clockwise until link 37 has pulled pylon support spindle 27 to rotate clockwise into helicopter mode.

It is important to note that all of the detail drawings of pylon-conversion actuation system 21 have been of actuation system 21 as deployed on left wing 15 of aircraft 11. It is to be understood that actuation system 21 is equally adapted for placement on right wing 15 of aircraft 11 and that actuation system 21 on right wing 15 would be a mirror image of actuation system 21 on left wing 15, and the direction of rotation needed to move actuation system 21 between the various modes would be the opposite of that discussed herein.

Referring now to FIG. 9 of the drawings, the graph shows a torque ratio curve 53 for the embodiment shown in FIGS. 3 through 8C. The torque ratio curve 53 is plotted with the torque ratio on the y-axis 55 and the conversion angle on the x-axis 57. The torque ratio is the torque applied to pylon support spindle 27 divided by the torque applied to rotary actuator 39. Therefore, a torque ratio value greater than 1.0 indicates a positive mechanical advantage in the system. The conversion angle is the relative position of pylon support spindle 27. A conversion angle of “0” indicates that pylon 17 is in airplane mode, whereas a conversion angle of “90” indicates that pylon 17 is in helicopter mode. Torque ratio curve 53 clearly shows that the above embodiment provides a mechanical advantage over the full range of motion, and this advantage is related to the ratio of the larger diameter of pylon support spindle 27 to the smaller diameter of actuator spindle 39. More importantly, the torque ratio increases at the extremes of the range of motion, i.e., near 0 degrees and near 90 degrees, and this increase in torque ratio shows an increase in mechanical advantage where it is needed most.

As described above, pylons 17 may be rotatably attached to aircraft 11 at locations other than at the ends of wings 15. For example, a pylon may be attached to the fuselage or may be located in an inboard portion of wing 15. Also, while link 37 is shown as a rigid, rod-like member, other types of linking means, such as a belt or chain, may be used to link rotary actuator 39 to pylon support spindle 27.

It is apparent that an invention with significant advantages has been described and illustrated. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof. 

1. A tiltrotor aircraft, comprising: a wing; a rotatable pylon carried by the wing, the pylon being secured to a pylon support spindle that extends into the wing; a rotary actuator; and a link connecting a radial portion of the actuator to a radial portion of the pylon support spindle, such that the pylon support spindle is rotated as the actuator is rotated.
 2. The tiltrotor aircraft according to claim 1, wherein a radial length of the radial portion of the actuator is less than a radial length of the radial portion of the pylon support spindle.
 3. The tiltrotor aircraft according to claim 1, wherein the link is curved.
 4. The tiltrotor aircraft according to claim 1, wherein the radial portion of the pylon support spindle is a bracket attached to the pylon support spindle, the link being pivotally attached to the bracket.
 5. The tiltrotor aircraft according to claim 1, wherein the actuator comprises an actuator spindle, the radial portion of the actuator being located on the actuator spindle.
 6. The tiltrotor aircraft according to claim 5, wherein an axis of rotation of the pylon support spindle and an axis of rotation of the actuator spindle are generally parallel.
 7. A tiltrotor aircraft, comprising: at least one wing; a pylon carried by the at least one wing, the pylon secured to a pylon support spindle that extends into the at least one wing; an actuator spindle located within the wing; and a link having a first end and a second end, the first end pivotally attached to a radial portion of the pylon support spindle and the second end pivotally attached to a radial portion of the actuator spindle.
 8. The tiltrotor aircraft according to claim 7, wherein the pylon support spindle has a diameter and the actuator spindle has a diameter less than the pylon support spindle.
 9. The tiltrotor aircraft according to claim 7, wherein the link is curved.
 10. The tiltrotor aircraft according to claim 7, wherein the radial portion of the pylon support spindle is a bracket attached to the pylon support spindle, the link being pivotally attached to the bracket.
 11. The tiltrotor aircraft according to claim 7, further comprising: a rotary actuator attached to the actuator spindle for applying torque to the actuator spindle.
 12. The tiltrotor aircraft according to claim 7, wherein an axis of rotation of the pylon support spindle and an axis of rotation of the actuator spindle are generally parallel.
 13. A method for rotating a pylon on a tiltrotor aircraft, wherein the pylon is rigidly attached to a pylon support spindle, the method comprising the steps of: selectively rotating an actuator spindle; and rotating the pylon support spindle using a link connecting the actuator spindle to the pylon support spindle, the actuator spindle being selectively rotated for positioning the pylon in a desired angular orientation.
 14. An actuation system for a pylon on a tiltrotor aircraft, the system comprising: a pylon support spindle for rigidly supporting the pylon; a rotary actuator; a link connecting a radial portion of the pylon support spindle to a radial portion of the rotary actuator, such that rotation of the rotary actuator produces rotation of the pylon support spindle.
 15. The actuation system according to claim 14, wherein the rotary actuator comprises an actuator spindle; and wherein the radial portion of the rotary actuator is located on the actuator spindle.
 16. An actuation system for a rotatable pylon of a tiltrotor aircraft, the system comprising: a first bellcrank operably connected to the pylon, the first bellcrank having a radial arm; a second bellcrank operably connected to an actuator, the second bellcrank having a radial arm; and a link connecting the arm of the first bellcrank to the arm of the second bellcrank, wherein operating the actuator causes rotation of the pylon. 